Notational expressivity; the case for and against the representation of internal subject structure in notational coding

The ways in which notation can be used to express the content of documents to which it relates are various. Ar the most superficial level notation can correspond to the hierarchical structure of the schedules or link to liter al components. The notation of compound concepts can express the structure and composition of the compound, and systems exist in which symbols denote the functional roles of the constituent elements and the relationships betw een them. Ar the highest level notation can be used to mirror the actual st ructure of chose entities which it represents, as in the case of mathematic al systems or chemical compounds. Methods of displaying these structures ar e examined, and the practicality in a documentary context is questioned, wi th particular reference to recent. revision work on the chemistry class of the Bliss Bibliographic Classification 2nd edition (BC2).